title: Blasticidin S inhibits translation by trapping deformed tRNA on the ribosome.
abstract: The antibiotic blasticidin S (BlaS) is a potent inhibitor of protein synthesis in bacteria and eukaryotes. We have determined a 3.4-Å crystal structure of BlaS bound to a 70S⋅tRNA ribosome complex and performed biochemical and single-molecule FRET experiments to determine the mechanism of action of the antibiotic. We find that BlaS enhances tRNA binding to the P site of the large ribosomal subunit and slows down spontaneous intersubunit rotation in pretranslocation ribosomes. However, the antibiotic has negligible effect on elongation factor G catalyzed translocation of tRNA and mRNA. The crystal structure of the antibiotic-ribosome complex reveals that BlaS impedes protein synthesis through a unique mechanism by bending the 3' terminus of the P-site tRNA toward the A site of the large ribosomal subunit. Biochemical experiments demonstrate that stabilization of the deformed conformation of the P-site tRNA by BlaS strongly inhibits peptidyl-tRNA hydrolysis by release factors and, to a lesser extent, peptide bond formation.
authors.affiliation: RNA Therapeutics Institute, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors.forename: Egor
authors.initials: E
authors.lastname: Svidritskiy
authors.forename: Clarence
authors.initials: C
authors.lastname: Ling
authors.forename: Dmitri N
authors.initials: DN
authors.lastname: Ermolenko
authors.forename: Andrei A
authors.initials: AA
authors.lastname: Korostelev
mesh_terms: D018360:Crystallography, X-Ray; D031541:Fluorescence Resonance Energy Transfer; D008958:Models, Molecular; D009705:Nucleosides / Q000494:pharmacology; D014176:Protein Biosynthesis / Q000187:drug effects*; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D016963:Thermus thermophilus / Q000378:metabolism
chemical_list: D009705:Nucleosides; C004500:blasticidin S; D012343:RNA, Transfer
keywords: peptidyl transfer; ribosome crystal structure; termination inhibitor; translation inhibitor; translation termination